'use strict';

/** Highest positive signed 32-bit float value */
var maxInt = 2147483647; // aka. 0x7FFFFFFF or 2^31-1

/** Bootstring parameters */
var base = 36;
var tMin = 1;
var tMax = 26;
var skew = 38;
var damp = 700;
var initialBias = 72;
var initialN = 128; // 0x80
var delimiter = '-'; // '\x2D'

/** Regular expressions */
var regexPunycode = /^xn--/;
var regexNonASCII = /[^\x20-\x7E]/; // unprintable ASCII chars + non-ASCII chars
var regexSeparators = /[\x2E\u3002\uFF0E\uFF61]/g; // RFC 3490 separators

/** Error messages */
var errors = {
  'overflow': 'Overflow: input needs wider integers to process',
  'not-basic': 'Illegal input >= 0x80 (not a basic code point)',
  'invalid-input': 'Invalid input'
};

/** Convenience shortcuts */
var baseMinusTMin = base - tMin;
var floor = Math.floor;
var stringFromCharCode = String.fromCharCode;

/*--------------------------------------------------------------------------*/

/**
 * A generic error utility function.
 * @private
 * @param {String} type The error type.
 * @returns {Error} Throws a `RangeError` with the applicable error message.
 */
function error(type) {
  throw new RangeError(errors[type]);
}

/**
 * A generic `Array#map` utility function.
 * @private
 * @param {Array} array The array to iterate over.
 * @param {Function} callback The function that gets called for every array
 * item.
 * @returns {Array} A new array of values returned by the callback function.
 */
function map(array, fn) {
  var result = [];
  var length = array.length;
  while (length--) {
    result[length] = fn(array[length]);
  }
  return result;
}

/**
 * A simple `Array#map`-like wrapper to work with domain name strings or email
 * addresses.
 * @private
 * @param {String} domain The domain name or email address.
 * @param {Function} callback The function that gets called for every
 * character.
 * @returns {Array} A new string of characters returned by the callback
 * function.
 */
function mapDomain(string, fn) {
  var parts = string.split('@');
  var result = '';
  if (parts.length > 1) {
    // In email addresses, only the domain name should be punycoded. Leave
    // the local part (i.e. everything up to `@`) intact.
    result = parts[0] + '@';
    string = parts[1];
  }
  // Avoid `split(regex)` for IE8 compatibility. See #17.
  string = string.replace(regexSeparators, '\x2E');
  var labels = string.split('.');
  var encoded = map(labels, fn).join('.');
  return result + encoded;
}

/**
 * Creates an array containing the numeric code points of each Unicode
 * character in the string. While JavaScript uses UCS-2 internally,
 * this function will convert a pair of surrogate halves (each of which
 * UCS-2 exposes as separate characters) into a single code point,
 * matching UTF-16.
 * @see `punycode.ucs2.encode`
 * @see <https://mathiasbynens.be/notes/javascript-encoding>
 * @memberOf punycode.ucs2
 * @name decode
 * @param {String} string The Unicode input string (UCS-2).
 * @returns {Array} The new array of code points.
 */
function ucs2decode(string) {
  var output = [];
  var counter = 0;
  var length = string.length;
  while (counter < length) {
    var value = string.charCodeAt(counter++);
    if (value >= 0xD800 && value <= 0xDBFF && counter < length) {
      // It's a high surrogate, and there is a next character.
      var extra = string.charCodeAt(counter++);
      if ((extra & 0xFC00) === 0xDC00) { // Low surrogate.
        output.push(((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000);
      } else {
        // It's an unmatched surrogate; only append this code unit, in case the
        // next code unit is the high surrogate of a surrogate pair.
        output.push(value);
        counter--;
      }
    } else {
      output.push(value);
    }
  }
  return output;
}

/**
 * Creates a string based on an array of numeric code points.
 * @see `punycode.ucs2.decode`
 * @memberOf punycode.ucs2
 * @name encode
 * @param {Array} codePoints The array of numeric code points.
 * @returns {String} The new Unicode string (UCS-2).
 */
function ucs2encode(array) {
  return String.fromCodePoint.apply(String, array);
}

/**
 * Converts a basic code point into a digit/integer.
 * @see `digitToBasic()`
 * @private
 * @param {Number} codePoint The basic numeric code point value.
 * @returns {Number} The numeric value of a basic code point (for use in
 * representing integers) in the range `0` to `base - 1`, or `base` if
 * the code point does not represent a value.
 */
function basicToDigit(codePoint) {
  if (codePoint - 0x30 < 0x0A) {
    return codePoint - 0x16;
  }
  if (codePoint - 0x41 < 0x1A) {
    return codePoint - 0x41;
  }
  if (codePoint - 0x61 < 0x1A) {
    return codePoint - 0x61;
  }
  return base;
}

/**
 * Converts a digit/integer into a basic code point.
 * @see `basicToDigit()`
 * @private
 * @param {Number} digit The numeric value of a basic code point.
 * @returns {Number} The basic code point whose value (when used for
 * representing integers) is `digit`, which needs to be in the range
 * `0` to `base - 1`. If `flag` is non-zero, the uppercase form is
 * used; else, the lowercase form is used. The behavior is undefined
 * if `flag` is non-zero and `digit` has no uppercase form.
 */
function digitToBasic(digit, flag) {
  //  0..25 map to ASCII a..z or A..Z
  // 26..35 map to ASCII 0..9
  return digit + 22 + 75 * (digit < 26) - ((flag !== 0) << 5);
}

/**
 * Bias adaptation function as per section 3.4 of RFC 3492.
 * https://tools.ietf.org/html/rfc3492#section-3.4
 * @private
 */
function adapt(delta, numPoints, firstTime) {
  var k = 0;
  delta = firstTime ? floor(delta / damp) : delta >> 1;
  delta += floor(delta / numPoints);
  for (/* no initialization */; delta > baseMinusTMin * tMax >> 1; k += base) {
    delta = floor(delta / baseMinusTMin);
  }
  return floor(k + (baseMinusTMin + 1) * delta / (delta + skew));
}

/**
 * Converts a Punycode string of ASCII-only symbols to a string of Unicode
 * symbols.
 * @memberOf punycode
 * @param {String} input The Punycode string of ASCII-only symbols.
 * @returns {String} The resulting string of Unicode symbols.
 */
function decode(input) {
  // Don't use UCS-2.
  var output = [];
  var inputLength = input.length;
  var i = 0;
  var n = initialN;
  var bias = initialBias;

  // Handle the basic code points: let `basic` be the number of input code
  // points before the last delimiter, or `0` if there is none, then copy
  // the first basic code points to the output.

  var basic = input.lastIndexOf(delimiter);
  if (basic < 0) {
    basic = 0;
  }

  for (var j = 0; j < basic; ++j) {
    // if it's not a basic code point
    if (input.charCodeAt(j) >= 0x80) {
      error('not-basic');
    }
    output.push(input.charCodeAt(j));
  }

  // Main decoding loop: start just after the last delimiter if any basic code
  // points were copied; start at the beginning otherwise.

  for (var index = basic > 0 ? basic + 1 : 0;
    index < inputLength; /* no final expression */) {

    // `index` is the index of the next character to be consumed.
    // Decode a generalized variable-length integer into `delta`,
    // which gets added to `i`. The overflow checking is easier
    // if we increase `i` as we go, then subtract off its starting
    // value at the end to obtain `delta`.
    var oldi = i;
    for (var w = 1, k = base; /* no condition */; k += base) {

      if (index >= inputLength) {
        error('invalid-input');
      }

      var digit = basicToDigit(input.charCodeAt(index++));

      if (digit >= base || digit > floor((maxInt - i) / w)) {
        error('overflow');
      }

      i += digit * w;
      var t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);

      if (digit < t) {
        break;
      }

      var baseMinusT = base - t;
      if (w > floor(maxInt / baseMinusT)) {
        error('overflow');
      }

      w *= baseMinusT;

    }

    var out = output.length + 1;
    bias = adapt(i - oldi, out, oldi === 0);

    // `i` was supposed to wrap around from `out` to `0`,
    // incrementing `n` each time, so we'll fix that now:
    if (floor(i / out) > maxInt - n) {
      error('overflow');
    }

    n += floor(i / out);
    i %= out;

    // Insert `n` at position `i` of the output.
    output.splice(i++, 0, n);

  }

  return String.fromCodePoint.apply(String, output);
}

/**
 * Converts a string of Unicode symbols (e.g. a domain name label) to a
 * Punycode string of ASCII-only symbols.
 * @memberOf punycode
 * @param {String} input The string of Unicode symbols.
 * @returns {String} The resulting Punycode string of ASCII-only symbols.
 */
function encode(input) {
  var output = [];

  // Convert the input in UCS-2 to an array of Unicode code points.
  input = ucs2decode(input);

  // Cache the length.
  var inputLength = input.length;

  // Initialize the state.
  var n = initialN;
  var delta = 0;
  var bias = initialBias;

  // Handle the basic code points.
  for (var i in input) {
    var currentValue = input[i];
    if (currentValue < 0x80) {
      output.push(stringFromCharCode(currentValue));
    }
  }

  var basicLength = output.length;
  var handledCPCount = basicLength;

  // `handledCPCount` is the number of code points that have been handled;
  // `basicLength` is the number of basic code points.

  // Finish the basic string with a delimiter unless it's empty.
  if (basicLength) {
    output.push(delimiter);
  }

  // Main encoding loop:
  while (handledCPCount < inputLength) {

    // All non-basic code points < n have been handled already. Find the next
    // larger one:
    var m = maxInt;
    for (var i0 in input) {
      var currValue = input[i0];
      if (currValue >= n && currValue < m) {
        m = currValue;
      }
    }

    // Increase `delta` enough to advance the decoder's <n,i> state to <m,0>,
    // but guard against overflow.
    var handledCPCountPlusOne = handledCPCount + 1;
    if (m - n > floor((maxInt - delta) / handledCPCountPlusOne)) {
      error('overflow');
    }

    delta += (m - n) * handledCPCountPlusOne;
    n = m;

    for (var j in input) {
      var currValue0 = input[j];
      if (currValue0 < n && ++delta > maxInt) {
        error('overflow');
      }
      if (currValue0 === n) {
        // Represent delta as a generalized variable-length integer.
        var q = delta;
        for (var k = base; /* no condition */; k += base) {
          var t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);
          if (q < t) {
            break;
          }
          var qMinusT = q - t;
          var baseMinusT = base - t;
          output.push(
            stringFromCharCode(digitToBasic(t + qMinusT % baseMinusT, 0))
          );
          q = floor(qMinusT / baseMinusT);
        }

        output.push(stringFromCharCode(digitToBasic(q, 0)));
        bias = adapt(delta,
                     handledCPCountPlusOne, handledCPCount === basicLength);
        delta = 0;
        ++handledCPCount;
      }
    }

    ++delta;
    ++n;

  }
  return output.join('');
}

/**
 * Converts a Punycode string representing a domain name or an email address
 * to Unicode. Only the Punycoded parts of the input will be converted, i.e.
 * it doesn't matter if you call it on a string that has already been
 * converted to Unicode.
 * @memberOf punycode
 * @param {String} input The Punycoded domain name or email address to
 * convert to Unicode.
 * @returns {String} The Unicode representation of the given Punycode
 * string.
 */
function toUnicode(input) {
  return mapDomain(input, function(string) {
    return regexPunycode.test(string) ?
      decode(string.slice(4).toLowerCase()) :
      string;
  });
}

/**
 * Converts a Unicode string representing a domain name or an email address to
 * Punycode. Only the non-ASCII parts of the domain name will be converted,
 * i.e. it doesn't matter if you call it with a domain that's already in
 * ASCII.
 * @memberOf punycode
 * @param {String} input The domain name or email address to convert, as a
 * Unicode string.
 * @returns {String} The Punycode representation of the given domain name or
 * email address.
 */
function toASCII(input) {
  return mapDomain(input, function(string) {
    return regexNonASCII.test(string) ?
      'xn--' + encode(string) :
      string;
  });
}

/*--------------------------------------------------------------------------*/

/** Define the public API */
var punycode = {
  /**
   * A string representing the current Punycode.js version number.
   * @memberOf punycode
   * @type String
   */
  'version': '2.0.0',
  /**
   * An object of methods to convert from JavaScript's internal character
   * representation (UCS-2) to Unicode code points, and back.
   * @see <https://mathiasbynens.be/notes/javascript-encoding>
   * @memberOf punycode
   * @type Object
   */
  'ucs2': {
    'decode': ucs2decode,
    'encode': ucs2encode
  },
  'decode': decode,
  'encode': encode,
  'toASCII': toASCII,
  'toUnicode': toUnicode
};

module.exports = punycode;
